The present invention relates to an electromagnetic actuator applicable to an electromagnetic appliance such as an electromagnetic valve.
An example of a prior art relevant to the present invention has been shown in the U.S. Pat. No. 4,156,506, the British Pat. No. 1,599,525 or the West German patent Laid Open Publication No. 2,812,739. In this prior art reference, there are provided a disk made of magnetic material and serving as a valve for opening or closing a fuel outlet, and an electromagnet fixedly mounted so that its pole-face is opposed to the disk. The disk receives the pressure of fuel so as to close the fuel outlet. The electromagnet has a core member which has a substantially flat plane opposit to the disk. In the flat plane of the core member, a plurality of grooves are formed in concentric circles as an example. A winding is disposed in the grooves so that directions of current in each groove are reversed alternately, i.e. the direction of current in one groove is different from the direction of current in an adjacent groove of said one groove. In such construction, an opening of the fuel outlet is effected by attracting the disk by means of the excitation of the electromagnet, while a closing of the fuel outlet is effected by pushing back the disk to the close position by means of the fuel pressure under the non-excitation of the electromagnet.
However, said prior art has the disadvantage that the response speed is rather slow, since it is necessary to attract the disk against the fuel pressure and the fluid resistance, and the closing operation depends on the fuel pressure. Therefore, there is a fear that a desired response cannot be achieved particularly in those cases that a high speed response is required.